JOHN GIANNICCHI / SCIENCE PHOTO LIBRARY JOHN GIANNICCHI / SCIENCE PHOTO LIBRARY
Human ovum. Coloured scanning electron micrograph of a single human ovum (egg). Mature human ova develop in the ovaries from primordial follicles that although formed between the 4th and 7th month of foetal development, remain dormant until sexual maturity. In each ovarian cycle up to 20 primordial follicles are activated to form primary follicles; normally only one will reach full maturity and be released at ovulation.
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